Methods and systems for dynamically controlling operations in a non-volatile memory to limit power consumption

ABSTRACT

Systems and methods are disclosed for limiting power consumption of a non-volatile memory (NVM) using a power limiting scheme that distributes a number of concurrent NVM operations over time. This provides a “current consumption cap” that fixes an upper limit of current consumption for the NVM, thereby eliminating peak power events. In one embodiment, power consumption of a NVM can be limited by receiving data suitable for use as a factor in adjusting a current threshold from at least one of a plurality of system sources. The current threshold can be less than a peak current capable of being consumed by the NVM and can be adjusted based on the received data. A power limiting scheme can be used that limits the number of concurrent NVM operations performed so that a cumulative current consumption of the NVM does not exceed the adjusted current threshold.

CROSS-REFERENCE TO RELATED APPLICATION

This is a continuation of commonly-assigned U.S. Publication No.2012/0023346, which is fully incorporated herein by reference.

FIELD OF THE INVENTION

This can relate to dynamically controlling operations in a non-volatilememory, such as a NAND flash memory, to limit power consumption.

BACKGROUND OF THE DISCLOSURE

Electronic systems are becoming more and more complex and areincorporating more and more components. As such, power demands for thesesystems continue to be a concern. In particular, because many of thecomponents in a system may operate at the same time, the system cansuffer from power or current spikes. This effect may be particularlypronounced when various system components are each performing high-poweroperations concurrently.

A flash memory system, which is commonly used for mass storage inconsumer electronics, is one example of a system in which powerconsumption is a concern. In heavy usage, the flash system canexperience elevated levels of power events, referred to herein as peakpower events. A peak power event may occur when each die in the flashmemory system is being accessed simultaneously. Systems that use flashmemory systems are designed to handle such peak power events (i.e.,maintain sufficient power resources to satisfy the power demand of peakpower events). However, peak power events can be relatively infrequent,and the average power consumption of the flash system can besubstantially less than peak power. Thus, as a result, these systems aredesigned to have elevated levels of power on reserve even though theelevated power level is not always needed.

SUMMARY OF THE DISCLOSURE

Systems and methods are disclosed for limiting power consumption of anon-volatile memory (NVM) using a power limiting scheme that distributesa number of concurrent NVM operations over time. This provides a“current consumption cap” that fixes an upper limit of currentconsumption for the NVM, thereby eliminating peak power events.

In one embodiment, power consumption of a NVM can be limited byreceiving data suitable for use as a factor in adjusting a currentthreshold from at least one of a plurality of system sources. Thecurrent threshold can be less than a peak current capable of beingconsumed by the NVM and can be adjusted based on the received data. Apower limiting scheme can be used that limits the number of concurrentNVM operations performed so that a cumulative current consumption of theNVM does not exceed the adjusted current threshold. In one embodiment,the power limiting scheme can be a reactive power limiting scheme thatuses feedback data provided by the NVM to determine when each NVMoperation is complete. In another embodiment, the power limiting schemecan be a predictive power limiting scheme that predicts how long eachNVM operation will take to complete.

BRIEF DESCRIPTION OF THE DRAWINGS

The above and other aspects and advantages of the invention will becomemore apparent upon consideration of the following detailed description,taken in conjunction with accompanying drawings, in which like referencecharacters refer to like parts throughout, and in which:

FIG. 1 is a schematic view of an electronic device configured inaccordance with various embodiments of the invention;

FIG. 2A is a schematic view of an illustrative system including a hostprocessor and a managed non-volatile memory package configured inaccordance with various embodiments of the invention;

FIG. 2B is a schematic view of an illustrative system including a hostprocessor and a raw non-volatile memory package configured in accordancewith various embodiments of the invention;

FIG. 2C is a graph illustrating a current consumption profile of a NMVpackage in accordance with various embodiments of the invention;

FIG. 3 is an illustrative block diagram showing in more detail a portionof a NVM package in accordance with various embodiments of theinvention;

FIG. 4A shows illustrative cumulative current consumption profile of alldie in a NVM package being controlled by a prior art system;

FIG. 4B shows illustrative cumulative current consumption profile of alldie in a NVM package being controlled by a system according to variousembodiments of the invention;

FIG. 5 shows an illustrative block diagram of power level selectioncircuitry in accordance with various embodiments of the invention; and

FIGS. 6-12 show several timing diagrams and flowcharts associated withpower limiting schemes in accordance with various embodiments of theinvention.

DETAILED DESCRIPTION OF THE DISCLOSURE

FIG. 1 is a schematic view of electronic device 100. In someembodiments, electronic device 100 can be or can include a portablemedia player (e.g., an iPod™ made available by Apple Inc. of Cupertino,Calif.), a cellular telephone (e.g., an iPhone™ made available by AppleInc.), a pocket-sized personal computer, a personal digital assistance(“PDA”), a desktop computer, a laptop computer, and any other suitabletype of electronic device.

Electronic device 100 can include system-on-a-chip (“SoC”) 110,non-volatile memory (“NVM”) 120, and power level selection circuitry130. Non-volatile memory 120 can include a NAND flash memory based onfloating gate or charge trapping technology, NOR flash memory, erasableprogrammable read only memory (“EPROM”), electrically erasableprogrammable read only memory (“EEPROM”), Ferroelectric RAM (“FRAM”),magnetoresistive RAM (“MRAM”), any other known or future types ofnon-volatile memory technology, or any combination thereof. NVM memory120 can include one or more dies that can be organized into “blocks,”which are the smallest units of erase, and further organized into“pages,” which are the smallest programmable and readable units. In someembodiments, NVM 120 can include multiple integrated circuits, whereeach integrated circuit may have multiple blocks. The blocks fromcorresponding integrated circuits (e.g., blocks having the same positionor block number) may form “super blocks.” Each memory location (e.g.,page or block) of NVM 120 can be addressed using a physical address(e.g., a physical page address or physical block address).

Power level selection circuitry 130 can set a power level that limits amaximum quantity of power or current that can be consumed by NVM 120.The power level can include a voltage level, a current level, or both.Circuitry 130 can be operative to select a power level based on anynumber of factors. These factors can include, for example, poweravailable from a power source (e.g., available battery power), powerloads required by various components in device 100 (e.g., SoC controlcircuitry 112), and temperature of device 100. Although circuitry 130 isshown to be illustratively connected to SoC 110 and NVM 120, it isunderstood that circuitry 130 can be connected to any component ofdevice 100. Additional details of circuitry 130 are provided below inconnection the description accompanying FIG. 5.

FIG. 1, as well as later figures and various disclosed embodiments, maysometimes be described in terms of using flash technology. However, thisis not intended to be limiting, and any other type of non-volatilememory can be implemented instead. Electronic device 100 can includeother components, such as a power supply or any user input or outputcomponents, which are not depicted in FIG. 1 to prevent overcomplicatingthe figure.

System-on-a-chip 110 can include SoC control circuitry 112, memory 114,and NVM interface 118. SoC control circuitry 112 can control the generaloperations and functions of SoC 110 and the other components of SoC 110or device 100. For example, responsive to user inputs and/or theinstructions of an application or operating system, SoC controlcircuitry 112 can issue read or write commands to NVM interface 118 toobtain data from or store data in NVM 120. For clarity, data that SoCcontrol circuitry 112 may request for storage or retrieval may bereferred to as “user data,” even though the data may not be directlyassociated with a user or user application. Rather, the user data can beany suitable sequence of digital information generated or obtained bySoC control circuitry 112 (e.g., via an application or operatingsystem).

SoC control circuitry 112 can include any combination of hardware,software, and firmware, and any components, circuitry, or logicoperative to drive the functionality of electronic device 100. Forexample, SoC control circuitry 112 can include one or more processorsthat operate under the control of software/firmware stored in NVM 120 ormemory 114.

Memory 114 can include any suitable type of volatile or non-volatilememory, such as dynamic random access memory (“DRAM”), synchronousdynamic random access memory (“SDRAM”), double-data-rate (“DDR”) RAM,cache memory, read-only memory (“ROM”), or any combination thereof.Memory 114 can include a data source that can temporarily store userdata for programming into or reading from non-volatile memory 120. Insome embodiments, memory 114 may act as the main memory for anyprocessors implemented as part of SoC control circuitry 112.

NVM interface 118 may include any suitable combination of hardware,software, and/or firmware configured to act as an interface or driverbetween SoC control circuitry 112 and NVM 120. For any software modulesincluded in NVM interface 118, corresponding program code may be storedin NVM 120 or memory 114.

NVM interface 118 can perform a variety of functions that allow SoCcontrol circuitry 112 to access NVM 120 and to manage the memorylocations (e.g., pages, blocks, super blocks, integrated circuits) ofNVM 120 and the data stored therein (e.g., user data). For example, NVMinterface 118 can interpret the read or write commands from SoC controlcircuitry 112, perform wear leveling, and generate read and programinstructions compatible with the bus protocol of NVM 120.

While NVM interface 118 and SoC control circuitry 112 are shown asseparate modules, this is intended only to simplify the description ofthe embodiments of the invention. It should be understood that thesemodules may share hardware components, software components, or both. Forexample, a processor implemented as part of SoC control circuitry 112may execute a software-based memory driver for NVM interface 118.Accordingly, portions of SoC control circuitry 112 and NVM interface 118may sometimes be referred to collectively as “control circuitry.”

FIG. 1 illustrates an electronic device where NVM 120 may not have itsown controller. In other embodiments, electronic device 100 can includea target device, such as a flash or SD card, that includes NVM 120 andsome or all portions of NVM interface 118 (e.g., a translation layer,discussed below). In these embodiments, SoC 110 or SoC control circuitry112 may act as the host controller for the target device. For example,as the host controller, SoC 110 can issue read and write requests to thetarget device.

FIGS. 2A and 2B are schematic views of systems, which are examples ofvarious embodiments of embodiment 100 of FIG. 1. Looking first to FIG.2A, system 200 can include host processor 210 and at least onenon-volatile memory (“NVM”) package 220. Host processor 210 andoptionally NVM package 220 can be implemented in any suitable hostdevice or system, such as a portable media player (e.g., an iPod™ madeavailable by Apple Inc. of Cupertino, Calif.), a cellular telephone(e.g., an iPhone™ made available by Apple Inc.), a pocket-sized personalcomputer, a personal digital assistance (“PDA”), a desktop computer, ora laptop computer.

Host processor 210 can include one or more processors or microprocessorsthat are currently available or will be developed in the future.Alternatively or in addition, host processor 210 can include or operatein conjunction with any other components or circuitry capable ofcontrolling various operations of memory system 200 (e.g.,application-specific integrated circuits (“ASICs”)). In aprocessor-based implementation, host processor 210 can execute firmwareand software programs loaded into a memory (not shown) implemented onthe host. The memory can include any suitable type of volatile memory(e.g., cache memory or random access memory (“RAM”), such as double datarate (“DDR”) RAM or static RAM (“SRAM”)). Host processor 210 can executeNVM driver 212, which may provide vendor-specific and/ortechnology-specific instructions that enable host processor 210 toperform various memory management and access functions for non-volatilememory package 220. Host processor 210 can perform any of the functionsof SoC 110 (of FIG. 1).

Host processor 210 can also execute power capping module 214, which maybe implemented as part of NVM driver 212. Power capping module 214 mayoperate as the power consumption controller of NVM package 220, and canimplement various power limiting schemes in accordance with variousembodiments of the invention. These power limiting schemes can cap thepower consumed by NVM package 220 by controlling the number of die 224that can be simultaneously accessed. The various power limiting schemesaccording to embodiments of the invention are discussed in more detailbelow.

NVM package 220 may be a ball grid array (“BGA”) package or othersuitable type of integrated circuit (“IC”) package. NVM package 220 maybe managed NVM package. In particular, NVM package 220 can include NVMcontroller 222 coupled to any suitable number of NVM dies 224. NVMcontroller 222 may include any suitable combination of processors,microprocessors, or hardware-based components (e.g., ASICs), and mayinclude the same components as or different components from hostprocessor 210. NVM controller 222 may share the responsibility ofmanaging and/or accessing the physical memory locations of NVM dies 224with NVM driver 212. Alternatively, NVM controller 222 may performsubstantially all of the management and access functions for NVM dies224. Thus, a “managed NVM” may refer to a memory device or package thatincludes a controller (e.g., NVM controller 222) configured to performat least one memory management function for a non-volatile memory (e.g.,NVM dies 224). Memory management and access functions that may beperformed by NVM controller 222 and/or host processor 210 for NVM dies224 can include issuing read, write, or erase instructions andperforming wear leveling, bad block management, garbage collection,logical-to-physical address mapping, SLC or MLC programming decisions,applying error correction or detection, and data queuing to set upprogram operations.

NVM package 220 can include power capping module 223, which can beexecuted by NVM controller 222. Power capping module 223 can have thesame operating capabilities as power capping module 214. In someembodiments, both power capping modules 214 and 223 can be included insystem 200. In this embodiment, modules 214 and 223 may work together toimplement a power limiting scheme according to an embodiment of theinvention. For example, module 214 may function as a master and module223 may function as a slave. In another embodiment, system 200 caninclude power capping module 214, but not power capping module 223. Inyet another embodiment, system 200 can include power capping module 223,but not power capping module 214.

NVM dies 224 may be used to store information that needs to be retainedwhen memory system 200 is powered down. As used herein, and depending oncontext, a “non-volatile memory” can refer to NVM dies in which data canbe stored, or may refer to a NVM package that includes the NVM dies.

Referring now to FIG. 2B, a schematic view of system 250 is shown, whichmay be an example of another embodiment of electronic device 100 ofFIG. 1. System 250 may have any of the features and functionalitiesdescribed above in connection with system 200 of FIG. 2A. In particular,any of the components depicted in FIG. 2B may have any of the featuresand functionalities of like-named components in FIG. 2A, and vice versa.

System 250 can include host processor 260 and non-volatile memorypackage 270. Unlike memory system 200 of FIG. 2A, NVM package 270 doesnot include an embedded NVM controller, and therefore NVM dies 274 maybe managed entirely by host processor 260 (e.g., via NVM driver 262).Thus, non-volatile memory package 270 may be referred to as a “raw NVM.”A “raw NVM” may refer to a memory device or package that may be managedentirely by a host controller or processor (e.g., host processor 260)implemented external to the NVM package. Host processor 260 may performany of the other memory management and access functions discussed abovein connection with host processor 210 and NVM controller 222 of FIG. 2A.In addition, host processor 260 may perform any of the functions of SoC110 (of FIG. 1).

Host processor 260 can also execute power capping module 264, which maybe implemented as part of NVM driver 262. Power capping module 264 canhave the same operating capabilities as power capping module 214 (FIG.2A).

With continued reference to both FIGS. 2A and 2B, NVM controller 222(FIG. 2A) and host processor 260 (e.g., via NVM driver 262) (FIG. 2B)may each embody the features and functionality of SoC 110 discussedabove in connection with FIG. 1, and NVM dies 224 and 274 may embodyrespective power consumption profiles that may be ascertained usingvarious embodiments of the invention. In particular, NVM dies 224 (FIG.2A) and 274 (FIG. 2B) may each have a peaky current profile, where thehighest peaks occur when a die is performing its most power-intensiveoperations. In flash memory embodiments, an example of such apower-intensive operation is a sensing operation (e.g., current sensingoperation), which may be used when reading data stored in memory cells.Such sensing operations may be performed, for example, responsive toread requests from a host processor and/or a NVM controller whenverifying that data was properly stored after programming.

FIG. 2C shows illustrative current consumption profile 290. Currentconsumption profile 290 gives an example of the current consumption of aNVM die (e.g., one of NVM dies 224 or 274) during a verification-typesensing operation. With several peaks, including peaks 292 and 294,current consumption profile 290 illustrates how peaky averification-type sensing operation may be. These verification-typesensing operations may be of particular concern, as these operations maybe likely to occur across multiple NVM dies at the same time (i.e., dueto employing parallel writes across multiple dies). Thus, if not managedby NVM controller 222 (FIG. 2A) or host processor 260 (FIG. 2B), thepeaks of different NVM dies may overlap and the total current sum may beunacceptably high. This situation may occur with other types ofpower-intensive operations, such as erase and program operations. Thus,when each die is simultaneously accessed (e.g., by way of a program,read, erase, or a combination thereof), the cumulative currentconsumption profile can be significantly higher than that of a singledie.

FIG. 3 is an illustrative block diagram showing in more detail a portionof a NVM package in accordance with an embodiment of the invention. FIG.3 shows how data can be transferred from data source 310 to buffer 320,and then from buffer 320 to one of pages 334, which resides in one ofblocks 332 of die 330, during a write operation. A write operation caninclude two parts: (1) a buffer operation, which is a transfer of datafrom data source 310 to buffer 320, and (2) a program operation, whichis a transfer of data from buffer 320 to die 310. Both parts may have atime component and a power consumption component. The bufferingoperating and the time required to fully perform it is referred toherein as Tbuff. The programming operation and the time required tofully perform it is referred to herein as Tprog.

The buffer and program parts of a write operation are illustrated intiming diagram 350. Diagram 350 shows a write operation starting attime, t0, and ending at time, t1. The buffer part may occupy arelatively small portion of the overall write operation, starting at t0and ending at t1, whereas the program part may occupy a relatively largeportion of the write operation, starting at t1 and ending at t1. Diagram350 also shows illustrative power consumption for the buffer and programparts. The program part consumes substantially more power than thebuffer part.

Data source 310 can be a black box representation of any source of data.For example, the data source can be data bus lines that route data toand from the NVM package. Data source 310 may receive data from a hostprocessor such as host processor 210 or 260 of FIGS. 2A and 2B.

Buffer 320 can be any suitable structure for temporarily storing data.For example, buffer 320 may be a register. Buffer 320 may be usedbecause it can receive and store data at a much faster rate than die330. Thus, buffer 320 enables a NVM interface to dispatch data torespective dies for temporary and fast storage (in buffer 320), therebyfreeing up the data lines for further data transfer. If buffer 320 werenot present, the data lines would be busy until all the data was writtento die 330.

Die 330 can include a predetermined number of physical blocks 332 andeach block can include a predetermined number of pages 334. Pages andblocks represent physical locations of memory cells within die 330.Cells within the pages or blocks can be accessed using addressingcircuitry (not shown) associated with the NVM package in which the cellsreside. Typically, only one block per die can be accessed at any giventime. In some embodiments, a die may be divided into multiple planes,where blocks in each plane of the die can be simultaneously accessed.

In some embodiments, blocks from two or more dies can be virtuallylinked together to form a superblock. Blocks need not be in the same rowof each die to be virtually linked as a superblock. In fact blocks maybe chosen randomly from two or more dies to form a superblock. In someembodiments, blocks may be chosen from two or more planes, in whichblocks in each plane are simultaneously accessible. Superblocks provideoperational parallelism, thereby enabling programming, reading, anderase operations to be performed on blocks located in different planesin parallel. In another embodiment, pages from two or more dies orplanes may be virtually linked together to form superpages. Atranslation layer being implemented in an NVM interface may keep trackof superblocks or superpages.

Feedback line 340 can provide information relating to operation of die330 and/or buffer 320. For example, feedback line 340 can providefeedback information such as when the buffer part and program part ofthe write operation are complete, the number of pulses required toprogram a page, a voltage signal, a voltage range, or any otherinformation relating to operation of die 300. It is understood that thetime and power of any part of a write operation can be resolved down tothe die, region of the die, block, or page (e.g., lower page or upperpage), and that any of this information may be provided on feedback line340. The information in feedback line 340 may be provided to an NVMcontroller (e.g., NVM controller 222) and/or a host processor, or moreparticularly to a power capping module.

It is understood that although the NVM operation discussed in FIG. 3relates to programming operations, other NVM operations such as read anderase can exhibit similar timing and power consumption parameters. Forexample, a read operation may have a read part and a buffer part. Theread part may consume more power than the buffer part and it may alsotake longer to perform.

FIG. 4A shows illustrative cumulative current consumption profile 410 ofall die in a NVM package being controlled by a prior art system. Profile410 may be produced in a system that does not employ a power limitingscheme. As a result, current profile 410 may include instances of peakcurrent consumption, as indicated by peaks 412 and 414. Since such aprior art system permits peak power events to occur, it has to bedesigned to accommodate such events. This places an unnecessary designrestraint on the system, thereby forcing it to handle NVM events thatreach peak current and to have sufficient power on reserve to meet thepeak current requirement. Moreover, because peak current events arerelatively infrequent, the average current consumption is below peakcurrent, as shown. This disparity in peak current and the averagecurrent results in excessive current overhead being allocated to the NVMpackage. Embodiments according to the invention overcome the deficiencyof FIG. 4A.

FIG. 4B shows illustrative cumulative current consumption profile 420 ofall die in a NVM package being controlled by a system according to anembodiment of the invention (e.g., system 100, system 200, or system250). Profile 420 is produced in a system that uses a power limiting orcurrent liming scheme. This scheme may cap current consumption, therebypreventing the instantaneous current from exceeding a current threshold.By capping current, peaks 422 and 424 are not permitted toinstantaneously consume as much current they would have otherwiseconsumed if not limited by the current threshold. As shown, peaks 422and 424 may be flattened because the number of concurrent NVM operationsis being limited by a power limiting scheme according to an embodimentof the invention. Thus, NVM events having concurrent operational load,which would otherwise exceed the current threshold if permitted tooperate without limit, are prevented from operating as such and aredistributed over time to ensure that the current consumption does notexceed the threshold. Techniques for limiting concurrent operation ofNVM events are discussed below in more detail in connection with thedescription accompanying FIGS. 6-12.

Use of a power limiting scheme can reduce the power overhead burden onthe NVM package. This can enable the system to allocate power resourcesto other components within the system because the current threshold setby the power limiting scheme can set the maximum power draw by the NVMpackage. In some embodiments, the power limiting scheme may vary thecurrent threshold depending on various system parameters. For example,if other components in the system such as a processor are relativelyidle, the current threshold for the NVM package can be increased topermit additional concurrent NVM operations. When the other componentsbecome relatively active, the current threshold for the NVM can bedecreased.

FIG. 5 shows an illustrative block diagram of power level selectioncircuitry 510 operative to provide and dynamically vary a currentthreshold based on inputs received from power supply monitoringcircuitry 512, load monitoring circuitry 514, temperature monitoringcircuitry 516, and NVM power consumption data 518. Selection circuitry510 may provide the current threshold to a NVM interface (e.g., NVMinterface 118) or an NVM package (e.g., NVM 120).

Power supply monitoring circuitry 512 can monitor an available powerlevel with the system and provide its data to power level selectioncircuitry 510. For example, circuitry 512 may monitor the energy levelof a battery. As another example, circuitry 512 may detect whether thesystem is receiving power from an external source such as a laptop orpower brick. Moreover, when the system is receiving external power,circuitry may indicate to power level selection circuitry how much poweris being received (e.g., 500 mAmps from a laptop or 1 Amp from a powerbrick). Load monitoring circuitry 514 can monitor a real-time load ofvarious components (e.g., processor, memory, backlight, LCD, userinterface, etc.) within the system. Circuitry 514 can also predict theload of the components based on, for example, command queues existingwithin the system. Temperature monitoring circuitry 516 can monitor thetemperature of the system.

NVM power consumption data 518 may specify how much power can beconsumed by the NVM package. The power consumption resolution of the NVMpackage may vary from relatively specific (e.g., power or currentconsumption of an upper page) to relatively general (e.g., powerconsumption of a particular die). Using this data, selection circuitry510 can determine how many concurrent NVM operations can be performedfor a given current threshold. Data 518 may be derived, for example,from NVM package vendors or from testing that determines powerconsumption of the NVM package. An example of a test for determiningpower consumption of NVM packages can be found U.S. patent applicationSer. No. 12/843,438, filed Jul. 26, 2010, entitled “Peak PowerValidation Methods and Systems for Non-Volatile Memory,” the disclosureof which is incorporated by reference herein in its entirety.

Selection circuitry 510 can balance the data it receives and set thecurrent threshold accordingly. For example, if supplied power is above apredetermined power threshold, the system load is below a predeterminedload threshold, and the temperature is below a predetermined temperaturethreshold, circuitry 510 may select a relatively high current threshold.As another example, if the supplied power is below a predetermined powerthreshold, the system load is above a predetermined load threshold, andthe temperature is below a predetermined temperature threshold,circuitry 510 may select a relatively low current threshold. It isunderstood that theses examples are merely illustrative and thatcircuitry 510 may receive additional inputs beyond those discussedherein as factors for dynamically varying the current threshold.

Referring now to FIGS. 6-12, several techniques for limiting powerconsumption in NVM operations are discussed. Each technique makesreference to the time to buffer and time to program, as previouslydiscussed above in FIG. 3. The time to buffer will be referred to hereinas Tbuff and the time to program will be referred to herein as Tprog.Some of the FIGS. will include reference to dies, which are numbered.Tbuff and Tprog may be appended with a die number (e.g., Tprog1) toindicate which die the Tbuff and Tprog operation is associated. Forexample, Tprog1 refers to the time to program for die number 1.

FIG. 6 shows illustrative ideal, non-current limited, timing diagram610. Timing diagram 610 shows Tbuff and Tprog for two dies, labeled withnumbers 1 and 2. It is understood that additional dies can be shown, buthave been omitted to avoid overcomplicating the drawing. As shown, theNVM event begins with Tbuff1, and immediately following its completion,Tprog1 and Tbuff2 commence. After Tbuff2 is complete, Tprog2 commences.At this point, the current consumption is at its highest because bothTprog1 and Tprog2 are in concurrent operation. When Tprog1 is complete,the current consumption drops because only Tprog2 is being performed.Timing diagram 610 is ideal because no current threshold is imposed onthe NVM operations, thus allowing the current consumption of both die 1and 2 to stack up.

FIG. 7 shows illustrative current limited timing diagram 710 inaccordance with an embodiment of the invention. Timing diagram 710 mayadhere to a current threshold that effectively limits concurrent dieoperation to just one die. As shown, the NVM event begins with Tbuff1,and immediately following its completion, Tprog1 and Tbuff2 commence. Incontrast to FIG. 6, Tprog2 does not commence until after Tbuff2 andTprog1 are complete. Thus, delaying the start of Tprog2 until afterTprog1 is complete limits the current consumption, thereby adhering tothe current threshold. A dashed line representation of Tprog2 (operatingin an ideal mode) is provided for comparison.

FIG. 8A shows illustrative current limited timing diagram 810 operatingaccording to a reactive power limiting scheme in accordance with anembodiment of the invention. In this scheme, it is assumed that a Tprogoperation commences substantially immediately after the Tbuff operationis complete. This scheme uses feedback data to control dispatch (i.e.,commencement) of Tbuff and Tprog operations for each die. The feedbackdata can specify, for example, when Tprog for a given die is complete.Thus, for a given current threshold, it is known how many concurrentTprog operations can be performed. Using this knowledge, and thefeedback data, the reactive power limiting scheme can dispatch as manyconcurrent operations as possible for the current threshold.

Timing diagram 810 begins with Tbuff1, followed by Tprog1. After Tprog1is complete, feedback data indicating that Tprog1 is complete isprovided. After this feedback data is received, the reactive powerlimiting scheme can commence Tbuff2, which is immediately followed byTprog2. Although it is not shown in the FIG., there may be latency incommencement of Tbuff2 after Tprog1 is complete because of any delayassociated with time it takes for the feedback data to be received andprocessed.

FIG. 8B shows an illustrative flowchart of steps that may be performedby a reactive power limiting scheme in accordance with an embodiment ofthe invention. Beginning at step 820, a current threshold is received. Afeedback loop is provided to show that the current threshold can changedepending on various factors in the system. When a different currentthreshold is received, the power limiting scheme can account for thisdifference make the appropriate changes as necessary.

At step 830, a determination is made as to a maximum number ofconcurrent NVM operations, Cmax, that may be performed based on thereceived current threshold. At step 840, an over limit of queuedconcurrent NVM operations are received, the concurrent operation ofwhich would exceed the current threshold. At step 850, a first set ofthe queued NVM operations are dispatched, the first set including anumber of operations that do not exceed Cmax. The first set can takeinto account any prior dispatched NVM operations that have not yetreported Tprog completion. At step 860, feedback of Tprog completions ismonitored. Upon detection of a completed Tprog, another one of thequeued NVM operations can be dispatched, as indicated in step 870.

At step 880, a determination is made if any additional queued NVMoperations exist. If the determination is YES, the process may loop backto step 860. It is understood that additional NVM operations may bereceived that can add to the over limit of queued NVM operations,thereby further perpetuating the need to limit the number of concurrentoperations. If the determination is NO, the process can loop back tostep 820.

FIG. 9 shows illustrative current limited timing diagram 910 operatingaccording to a pipelined reactive power limiting scheme in accordancewith an embodiment of the invention. This scheme is similar to thereactive power limiting scheme discussed above in connection with FIGS.8A & 8B except that the Tbuff operations can be pipelined. However, theTprog operations do not automatically commence substantially immediatelyafter the Tbuff operations are complete. This scheme can increase thethroughput of NVM operations by eliminating the need to perform a Tbuffoperation substantially immediately prior to its corresponding Tprogoperation. That is, a Tbuff operation for a second die can be performedbefore or during the Tprog operation of a first die.

Timing diagram 910 starts with Tbuff1, and after Tbuff1 is complete,both Tprog1 and Tbuff2 can commence. Tbuff2 completes its operationbefore Tprog1 is complete, but pipeline reactive scheme does not permitTprog2 to commence until feedback is received indicating Tprog1 iscomplete. In another embodiment, Tbuff1 and Tbuff2 can commencetogether, but Tprog2 will not commence until Tprog1 is complete.

FIGS. 10A & 11A shows illustrative current limited timing diagramsoperating according to predictive power limiting schemes in accordancewith an embodiment of the invention. Predictive power limiting schemescan predict how long each NVM operation will take to complete, andbecause it is known how many concurrent Tprog operations can beperformed for a given current threshold, the predictive power limitingscheme can operate to dispatch as many concurrent operations aspossible. In contrast to the reactive power limiting schemes, predictivepower limiting schemes are not required to rely on feedback to determinewhen subsequent NVM operations can be dispatched. As its name implies,predictive power limiting predicts when a given NVM operation will becomplete and dispatches a NVM operation after the time period associatedwith that prediction ends.

The prediction of a NVM operation can include two parts: (1) time tobuffer prediction, Tbuff(p), and (2) time to program prediction,Tprog(p). Tbuff(p) and Tprog(p) are predictions of how long the actualTbuff and Tprog operations actually take. Selection of Tbuff(p) andTprog(p) can vary from conservative to aggressive. In other embodiments,context specific predictions can be selected (e.g., Tprog(p) may behigher for programming upper pages than for programming lower pages). Inyet another embodiment, a hybrid approach of using prediction withfeedback information may be implemented.

Referring now to FIG. 10A, an illustrative current limited timingdiagram 1010 operating according to a conservative predictive powerlimiting scheme in accordance with an embodiment of the invention isshown. In one embodiment, conservative predictions can ensure thatadequate time is allotted for each NVM operation such that it issubstantially reasonably assured that the actual Tbuff and Tprog timesare less than Tbuff(p) and Tprog(p). In another embodiment, conservativepredictions can be selected to ensure that Tbuff(p) is greater thanTprog. These approaches can provide a safety net to guard against, forexample, unexpected delays in Tprog, but at the cost of predicting moretime than actually needed for the operation to complete. Thus, there isa potential risk of predictive overhead time that can reduce throughputof concurrent NVM operations.

Timing diagram 1010 shows predictive timing parameters for two dies, andbecause conservative predictive parameters are selected, an assumptionis made that Tbuff takes a longer time to complete than Tprog. Inpractice, the opposite is true; Tprog generally always takes longer tocomplete than Tbuff. As shown, Tbuff(p1) and Tbuff(p2) are allottedgreater time for completion than Tprog(p1) and Tprog(p2). Referring nowto both FIG. A and FIG. 10B, timing diagram 1020 shows actual timingparameters for the two die operating according to the conservativepredictive power limiting scheme. The start of Tprog2 is keyed off ofthe completion of Tbuff(p2), and not the completion of Tprog1. Thus, byensuring that Tbuff(p2) is greater than Tprog1, there is no overlap ofTprog1 and Tprog2, thereby preventing an undesired concurrent operationof NVM operations.

FIG. 10C shows an illustrative flowchart of steps that may be taken toimplement a conservative predictive power limiting scheme in accordancewith an embodiment of the invention. Beginning at step 1022, a currentthreshold is received. A feedback loop is provided to show that thecurrent threshold can change depending on various factors in the system.When a different current threshold is received, any limitationassociated with the different current threshold is applied by predictivepower limiting scheme. At step 1030, a determination is made as to amaximum number of concurrent NVM operations, Cmax, that may be performedbased on the received current threshold.

At step 1040, the predictive scheme selects predictive timing parametersfor NVM operations. These parameters can include Tbuff(p) and Tprog(p)and can be uniformly applied to all NVM operations. For example, in oneembodiment, the time duration of Tbuff(p) may be greater than the timeduration Tprog(p). The actual values selected for predictive timingparameters may be derived from any suitable source. For example, theparameters may be based on NVM package vendor specifications, an averagetime duration of Tprog and/or Tbuff, or testing data. In someembodiments, the actual values selected for Tbuff(p) and Tprog(p) may bebased on maximum durations required for each of these NVM operations. Incontrast to an approach that selects actual values based on the averagedurations for these NVM operations, using maximum durations for Tbuff(p)and Tprog(p) can prevent a situation where a prior dispatched operationhas not yet completed before a next operation begins.

At step 1045, an over limit of queued concurrent NVM operations arereceived, the concurrent operation of which would exceed the currentthreshold if permitted to operate all at once. For ease of discussion,assume the queued NVM operations are received while at least one Tprogoperation is in progress. At step 1050, a determination is made as tohow many of the queued NVM operations can be dispatched such that thedispatched set does not exceed Cmax. The determination can take intoaccount any prior dispatched NVM operations that have already beendispatched but are still within a predicted timing parameter such asTbuff(p). For example, assume that 5 concurrent NVM operations can beperformed for the selected current threshold, and that one priordispatched NVM operation is outstanding, but not presumed to be completebecause the predicted time parameter (e.g., the Tbuff(p)) for the priordispatched operation has not expired. Operating under this assumption,the dispatched set can include 4 queued NVM operations. It is understoodthat while step 1050 or any subsequent step is being performed,additional NVM operations may be added to the queue.

At step 1055, Tbuff(p) parameters associated with the dispatched set ofqueued NVM operations are appended to the end of the Tbuff(p) parameterof a prior dispatched NVM operation. If there is more than one priordispatched NVM operation, the last in sequence prior dispatched NVMoperation may be the keyed off of NVM operation. In other words, thedispatched set Tbuff(p) parameters can commence when Tprog of the priordispatched NVM operation begins. Thus, appending the first set Tbuff(p)parameters in this manner ensures that Tprog of the prior dispatched NVMoperation is provided with sufficient time to complete its operationbefore the Tprog of the dispatched set begins.

At step 1060, the prior dispatched NVM operation is programmed into apage of the NVM package during the Tbuff(p) of the dispatched set. Atstep 1070, a determination is made if there are any remaining queued NVMoperations. If YES, the process reverts back to step 1050. If NO, theprocess reverts back to step 1022.

FIG. 11A shows illustrative current limited timing diagram 1110operating according to an aggressive predictive power limiting scheme inaccordance with an embodiment of the invention. In one embodiment, theaggressive scheme can assume that Tbuff is substantially constant foreach NVM operation and that Tprog may vary depending on one or morefactors. As such, the aggressive scheme can affix a constant to Tbuff(p)such as a time value typically associated with buffer operations, andthe scheme may use a sliding scale of predictive times for Tprog(p). Inaddition, the Tbuff operations may be pipelined and ready for the Tprogoperation as soon as the scheme permits. Commencement of Tprog for aconcurrent NVM operation (that would result in a cumulative powerconsumption that exceeds the current threshold if not limited by thisscheme) can be at the end of a Tprog(p) of a prior dispatched NVMoperation. This is in contrast to the conservative predictive approach,which commenced Tprog at the end of Tbuff(p).

The aggressive aspect of this scheme is provided by the sliding scale ofTprog(p). It is desirable to minimize Tprog(p), but not to an extentthat the actual Tprog operation exceeds Tprog(p). Tprog(p) can varybased on any number of factors. For example, Tprog(p) can vary based onthe current threshold, whether data is being programmed to a lower pageor an upper page, the region of die the data is to be programmed, thenumber of NVM operations in the over limit queue, or a combinationthereof.

For instance, the current consumed by a system may vary depending onwhether data is being programmed to a lower or upper page. Because upperpage programming generally takes longer than lower page programming, thecurrent consumption for upper page programming is correspondinglyhigher. Thus, a longer predictive time may be assigned to Tprog(p) forupper page programming than for lower page programming.

Timing diagram 1110 shows predictive Tbuff(p) and Tprog(p) for two dieoperating under a current threshold that only permits one concurrent NVMoperation. As shown, Tbuff(p1) and Tbuff(b2) to illustrate that bufferoperations can be pipelined. Tprog(p1) commences immediately afterTbuff(p1), and because only one concurrent NVM operation is permitted inthis example, Tprog(p2) keys off of the predictive end of Tprog(p1).Referring now to both FIG. 11A and FIG. 11B, timing diagram 1120 showsactual timing parameters for the two die operating according to theaggressive predictive power limiting scheme. The start of Tprog1 iskeyed off of the completion of Tbuff(p1), and the start of Tprog2 iskeyed off the completion of Tprog(p1).

FIGS. 11C and 11D show additional illustrative timing diagrams 1130 and1140, respectively, according to respective aggressive predictive powerlimiting schemes in accordance with embodiments of the invention. Timingdiagrams 1130 and 1140 show six concurrent NVM operations operatingunder a current threshold that permits only two concurrent NVMoperations. In addition, timing diagrams 1130 and 1140 show how thepredictive Tprog(p) from one NVM operation to another may vary (based onany suitable factors such as those discussed above). For example, intiming diagram 1130, NVM Tprog(p) operations 1, 3, and 5 are allottedless time than NVM Tprog(p) operations 2, 4, and 6. Whereas, as intiming diagram 1140, NVM Tprog(p) operations 1, 3, and 5 are allottedmore time than NVM Tprog(p) operations 2, 4, and 6. In timing diagrams1130 and 1140, each successive Tprog(p) operation is keyed off thecompletion of the prior Tprog(p) operation.

FIG. 11E shows an illustrative flowchart of steps that may be performedby an aggressive predictive power limiting scheme in accordance with anembodiment of the invention. This flowchart is similar in many respectsto the flowchart discussed above in connection with FIG. 10C, with theprinciple difference being that Tprog operations are keyed off of theend of Tprog(p) prediction.

Beginning at step 1142, each NVM operation is assigned a predictive timefor programming parameter (Tprog(p)). This parameter may vary dependingon various factors as discussed above. At step 1144, data associatedwith each NVM operation is buffered so that data is available forsubstantially immediate programming. That is, data for multiple NVMoperations can be stored in multiple respective buffers, but the datastored therein is not automatically programmed into a page of a die.

At step 1146, the start of a subsequent program operation of a NVMoperation is initiated at the end of a Tprog(p) of a prior NVMoperation. For example, assume that the subsequent program operation isTprog2 and that the predictive Tprog(p1) of prior program operationTprog1 ends at time t1. This assumes that program operation Tprog1 willbe complete by the time t1 (which is predicted by Tprog(p1)). Thus, thesubsequent program operation Tprog2 starts at time t1. In addition, thepredictive Tprog(p2) for program operation Tprog2 also starts at timet1. At step 1148, the buffered data is used to perform the programmingpart of the subsequent NVM operation.

FIG. 12 shows illustrative steps that may be practiced by a system usinga power limiting scheme in accordance with an embodiment of theinvention. Starting with step 1210, data suitable for use as a factor inadjusting a current threshold is received from a plurality of sources.The sources can include various monitoring circuitry that monitorscomponents and conditions associated with those components (e.g.,circuitry 512, 514, and 516 of FIG. 5). The source can also include datathat specifies operating parameters (e.g., NVM package peak powerconsumption) of various components of the system. The current thresholdmay set a maximum current consumption for a NVM package even though theNVM package is capable of consuming more power than that set by thethreshold. The current threshold can be less than a peak current capableof being consumed by the NVM.

At step 1220, the current threshold can be adjusted based on thereceived data. The system can initially set the current threshold to aminimum current threshold level. This level can ensure that the NVMpackage is able to meet a minimum threshold of performance. If thereceived data indicates that additional power can be provided to the NVMpackage, the current threshold can be adjusted upwards to take advantageof the additional power. When the received data indicates the additionalpower is no longer available, current threshold can be downward adjustedaccordingly. A feedback loop from step 1220 to step 1210 is provided toshow that the current threshold can be adjusted in real-time.

At step 1230, a power limiting scheme is used to limit the number ofconcurrent NVM operations so that a cumulative current consumption doesnot exceed the adjusted current threshold. The power limiting scheme canbe any one of the power limiting schemes discussed herein (e.g., one ofthe reactive or predictive power limiting schemes). In some embodiments,the system may switch between two or more power limiting schemes.

It should be understood that the steps included in flowcharts of FIGS.8B, 10C, 11E, and 12 are merely illustrative. Any of the steps may beremoved, modified, or combined, and any additional steps may be added,without departing from the scope of the invention.

The described embodiments of the invention are presented for the purposeof illustration and not of limitation.

What is claimed is:
 1. A method for reactively limiting powerconsumption of a non-volatile memory (NVM), the method comprising:receiving a current threshold; determining a maximum number ofconcurrent NVM operations that can be performed based on the currentthreshold; receiving an overlimit of queued concurrent NVM operations,the concurrent operation of which would have a cumulative currentconsumption that exceeds the current threshold; dispatching a first setof the queued NVM operations, the first set including a number of thequeued NVM operations that do not exceed the maximum number; monitoringfeedback data for at least partial completion of NVM operations, whereinthe feedback data comprises information on at least one of a bufferingpart of a NVM operation and a programming part of a NVM operation; anddispatching another one of the queued NVM operations based on thefeedback data.
 2. The method of claim 1, wherein a queued NVM operationcomprises a buffering part and a programming part, wherein thedispatching comprises: performing the programming part substantiallyimmediately after the buffering part is performed.
 3. The method ofclaim 1, wherein a queued NVM operation comprises a buffering part and aprogramming part, wherein the dispatching comprises: performing thebuffering part; and delaying performance of the programming part until acompleted NVM operation is monitored.
 4. The method of claim 1, whereinthe NVM is nand flash NVM and the current threshold being less than apeak current capable of being consumed by the nand flash NVM.
 5. Themethod of claim 1, further comprising: repeating the dispatching of anadditional queued NVM operation when a completed NVM operation ismonitored.
 6. The method of claim 1, wherein the dispatch is performedbased on feedback data regarding one of: a completed bufferingoperation, a completed programming operation and both a completedbuffering operation and a completed programming operation.
 7. Anelectronic device, comprising: non-volatile memory (NVM) having aplurality of dies and that is operative to perform a plurality ofconcurrent NVM operations, each NVM operation consuming a fixed quantityof current; power level selection circuitry operative to provide acurrent threshold based on data received from at least one of aplurality of device sources, the current threshold being less than apeak current capable of being consumed by the NVM; and power cappingcircuitry in operative communication with the NVM and the power levelselection circuitry, the power capping circuitry operative to: determinea maximum number of concurrent NVM operations that can be performedbased on the current threshold; receive an overlimit of queuedconcurrent NVM operations, the concurrent operation of which would havea cumulative current consumption that exceeds the current threshold;dispatch a first set of the queued NVM operations, the first setincluding a number of the queued NVM operations that do not exceed themaximum number; monitor feedback data for at least partial completion ofNVM operations, wherein the feedback data comprises information on atleast one of a buffering part of a NVM operation and a programming partof a NVM operation; and dispatch based on the feedback data.
 8. Themethod of claim 7, wherein a NVM operation comprises a buffering partand a programming part, wherein the power capping circuitry is operativeto: perform the programming part substantially immediately after thebuffering part is performed.
 9. The method of claim 7, wherein a NVMoperation comprises a buffering part and a programming part, wherein thepower capping circuitry is operative to: perform the buffering part; anddelay performance of the programming part until a completed NVMoperation is monitored.
 10. The method of claim 7, wherein the NVM isnand flash NVM and the current threshold is less than a peak currentcapable of being consumed by the nand flash NVM.
 11. The method of claim7, wherein the power capping circuitry is operative to: repeat thedispatching of an additional queued NVM operation when a completed NVMoperation is monitored.
 12. The method of claim 7, wherein the dispatchis performed based on feedback data regarding one of: a completedbuffering operation, a completed programming operation and both acompleted buffering operation and a completed programming operation.